To prevent global warming in recent years, it is desired to reduce emissions of greenhouse gases such as carbon dioxide and technologies are being developed for capturing carbon dioxide in a combustion exhaust gas emitted from an oxyfuel combustion boiler for a storage process in ocean or in the underground formation.
Such an oxyfuel combustion boiler comprises an oxygen introduction passage for introduction of oxygen to an air feed passage connected to a wind box on an inlet side of an oxyfuel combustion boiler body, and an exhaust gas circulation passage branched from an exhaust gas passage connected to an outlet side of the oxyfuel combustion boiler body for connection with the air feed passage. Upon start-up, air is introduced through the air feed passage to the oxyfuel combustion boiler body for combustion of fuel. After completion of the start-up, dampers, etc., disposed in the passages are switched to circulate an exhaust gas discharged from the oxyfuel combustion boiler body through the exhaust gas circulation passage to the oxyfuel combustion boiler body while oxygen is introduced through the oxygen introduction passage to the oxyfuel combustion boiler body to perform the oxyfuel combustion of the fuel while constraining reduction of oxygen concentration due to the circulation of the exhaust gas to thereby increase a concentration of carbon dioxide in the exhaust gas, the carbon dioxide being captured from a portion of the exhaust gas.
The oxyfuel combustion boiler comprises a pulverized coal burner which is composed of an oil burner and a pulverized coal feed passage, and an oxygen injection nozzle which supplies the pulverized coal feed passage with oxygen to mix and burn pulverized coal, etc., with air from the wind box (e.g., Patent Literature 1).
For example, Patent Literatures 2 to 5 describe techniques related to such an oxyfuel combustion boiler.    [Patent Literature 1] JP 07-318016A    [Patent Literature 2] JP 05-231609A    [Patent Literature 3] JP 2001-235103A    [Patent Literature 4] JP 05-168853A    [Patent Literature 5] JP 2007-147162A